1. Field of the Invention
The present invention relates to a light guide plate as a component of a plane light source apparatus used as a back-light of a variety of display devices.
2. Description of the Related Art
A light guide plate is one of optical members used in a plane light source apparatus installed in a variety of display devices, for example in a plane light source apparatus of an edge light mode, it plays a role of emitting a light from a light source introduced into the light guide plate while guiding the light in a perpendicular direction with respect to the direction in which the light is incident. In such a light guide plate, its overall emission surface serves as a direct light source of a variety of display devices, so it is required to be comprised of members having a high transparency to attain higher luminance, and to have less luminance spots on the luminescence surface to attain a unified distribution of a light emission amount.
Therefore, in the related art, materials, such as a polymethyl methacrylate (PMMA) and polycarbonate (PC) are used as materials of light guide plates, on the light reflection surface (reflector surface) of the light guide plate is devised to be formed recesses having a variety of shapes as a reflection means for attaining higher luminance, for example, it is known to form grooves causing less light losses when molding the light guide plate (The Japanese Unexamined Patent Publication 1990-165504). Also, there are known means for arranging grooves so that density of an arrangement pattern increases along with the distance from the light source, and for arranging to be a check pattern for further higher luminance (The Japanese Unexamined patent Publication 1994-250025 and 1993-216030).
However, with the materials of the related art, such as PMMA and PC, sufficient front luminance has not yet obtained even if the groove arrangement patterns as above are provided due to reasons of optical characteristics of a refractive index, transparency, etc. which the materials themselves have.
Further, in the PMMA, melting viscosity is high and fluidity is deteriorated at the time of injection molding, while in the PC, when a resin temperature is raised for promoting fluidity, it is liable that the resin hydrolyzes and bubbles. There have been harmful influences, such as generation of luminance spots, deterioration of the front face luminance, which are caused because transferability of a preferable groove shape cannot be obtained actually in a range where the arrangement of the reflection pattern is dense (being distant from the light source).
Furthermore, in recent years, as back-light units becoming thinner and lighter each year, the trend in the light guide plate is also shifting to be thinner and wider in area, and in terms of the shape, instead of a flat plate having a constant thickness, light guide plates of a wedge shape wherein the thickness becomes thinner as becoming distant from the light source are often in use in terms of higher luminance by an effective use of a light and a lighter weight. Thus, the PMMA and PC having a disadvantage in moldability have been coming to face a difficult situation in being used as a thin and wide light guide plate.
In addition to the above, in a wedge shaped light guide plate as above, since a region where the arrangement density of the grooves is increased is a region where the thickness of the plate becomes thinner, the PMMA, etc. are concerned about disadvantages that the plate strength declines due to provision of grooves and deformation while in use as a light guide plate (warps of the plate caused by shrink in the direction to the light emission surface having a small surface) becomes remarkable. There have been demands for a light guide plate material capable of overcoming such size deformation, fulfilling the strength, moldability, high luminance and low luminance spots and attaining to be thin and wide area.
Note that, as disclosed in the Japanese Unexamined Patent Publication 1995-43710, study on making the light guide plate thinner, improving luminance balance on the light emission surface, and reducing the luminance spots along with a luminance line by forming a plurality of grooves of an inversed V shape having projections protruding to outside on both sides of a V-shaped groove. It is also studied to form as one body a pattern of recesses and projections for reflection on the light reflection surface of the light guide plate and recesses and projections for light convergence on the surface of the light guide plate (The Japanese Unexamined Patent Publication 1996-179322).
An object of the present invention is to provide a light guide plate capable of solving the disadvantages of the related art, being superior in moldability, suppressing hygroscopic deformation little while in use, having sufficient strength, and being made thin and wide, and attaining high luminance and low luminance spots.
The present inventors studied diligently to attain the above objects and found that a light guide plate formed by using a polymeric resin having an alicyclic structure, wherein a reflection surface is formed as a reflection pattern recesses arranged so that the density increases along with the distance from a light source, has preferable moldability, transferability, size stability and strength even in the case of being thin and wide, and able to attain high luminance and low luminance spots, and the present invention was completed.
Namely, a light guide plate of the present invention is comprised of a polymeric resin having an alicyclic structure and has recesses for reflection formed on a light reflecting surface, the recesses being so arranged that the density of the recesses increases with the distance from a light source.
A light guide plate of the present invention is comprised of a polymeric resin having an alicyclic structure comprising recesses for reflection formed on a light reflection surface and projections formed respectively near edges of said recesses.
A light guide plate of the present invention is comprised of a polymeric resin having an alicyclic structure, wherein concave portions and convex portions for light convergence are formed integrally on the light emission surface.
The recesses may be formed for example in dots shape (concaves on a certain part) and may be continuously formed for example in a groove shape (concave on a continuous line). The sectional shape of the recesses may be for example V-shape, U-shape, square shape, etc. among them, the recesses is preferably a groove, more preferably a V-shaped groove. In this case, it is preferable that the V-shaped groove has an angle (xcex8) of 70xc2x0 to 150xc2x0 and a depth (H1) of 1 xcexcm to 1000 xcexcm.
In the case that the recesses are grooves, the direction of the grooves is not particularly limited, and may be formed to extend in the direction of approximately parallel direction with respect to a direction in which a light is incident, or extend in the direction of approximately vertical direction with respect to the same. It is preferably formed in the approximately vertical direction with respect to a direction in which a light is incident with respect to at any position on the light reflection surface. In this case, a length of the groove is preferably formed over the full width in the direction on the light reflection surface of the light guide plate.
It is preferable that projections formed respectively near edges of said recesses is further provided. And the ratio of the cross sectional areas of the recesses and the projections in this case is preferably 10:1 to 10:10. In the present invention, the cross sectional area of the recesses and the projection is calculated based on the light reflection surface of the light guide plate on which the recesses and projections are not formed. Also, the ratio is a ratio of a cross sectional area of the recess and that of the projection when one projection is formed near the edge of one recess. While, when a plurality of projections are arranged near the both side edges of one recess, it is a ratio of the cross sectional area of the recess and that of one of the plurality of projections arranged near the both side edges.
When the recess is in dot shape formed in a dispersed way, the projection is preferably formed at an edge thereof. While when the recess is a groove, the projection is preferably formed respectively near one side edge or near the both side edge, and more preferably formed on the both sides thereof. The projection is preferably a protruding portion.
The polymeric resin having an alicyclic preferably contains at least 10 wt % of repeating units composed of an alicyclic structure not having norbornenes structure in the repeating units composed of all alicyclic structures.
The light guide plate of the present invention is preferably molded by injection molding.
Preferably, concave portions and convex portions for light convergence are formed integrally on a light emission surface. The concave portions and convex portions for light convergence are not particularly limited as far as it serves as making the light emitted from the light emission surface of the light guide plate as close as possible to the front surface (0xc2x0), but preferably repeating units of a prism shape.
The polymeric resin having an alicyclic structure used in the present invention excels in moldability processing, such as fluidity and heat-resistence, of the resin while being molded, so recesses for reflection can be formed on the light reflection surface without any transfer deficiencies, and a light guide plate able to be made thin and wide, superior in optical characteristics, such as transparency. Accordingly, a light guide plate having high luminance by effectively utilizing a light (particularly, the front face luminance is remarkably improved), and little luminance spots can be provided. Also, the polymeric resin having an alicyclic structure is superior in strength physicality and has characteristics that size deformation by hygroscopic deformation is small, thus, even when reflection recesses are formed on a wedge shape wherein the thickness gradually gets thinner, size deformation by a warp, etc. at the time of being used is hard to occur and there is a small possibility that the light guide plate itself is damaged. Furthermore, the polymeric resin having an alicyclic structure has a small specific gravity comparing with the PMMA and PC, so the light guide plate can be made light, consequently, a back-light unit can be made light. Accordingly, the present invention can provide a light guide plate being superior in moldability, having little hygroscopic deformation and sufficient strength, able to be made thin and wide, and capable of attaining high luminance and low luminance spots.
Also, by forming the projection portion near an edge of said recess, luminance spots are further reduced.
Furthermore, by forming integrally concave portions and convex portions for light convergence on the light emission surface, it becomes unnecessary to provide a light convergence sheet separately from a light guide plate so assembly procedures of a back light unit can be simplified.
A xe2x80x9clight guide platexe2x80x9d in the present invention is not specifically limited the use, but indicates those which used in flat light source apparatuses used as a back-light of, for example, office-use and home-use products, such as personal computers of lap-top, notebook, book, palm-top and other types, mobile computers, word processors, electronic pocketbooks, electronic dictionaries, liquid crystal televisions to be hang on the wall, etc.; illumination signs; a display window of pinball machines, cellular phones, pagers and automatic teller machines; light tables, viewers and other display devices.
A light guide plate of the present invention may be either a flat shape having a constant thickness or for example a wedge shape wherein the thickness gradually gets thinner from one end to the other. When the light guide plate is flat, the thickness is normally 0.1 to 10 mm, preferably, 1 to 5 mm. While when the light guide plate is wedge shaped, the thickness of a thick part is normally 0.5 to 10 mm, preferably, 1 to 5 mm and the thickness of a thin part is normally 0.1 to 5 mm, preferably, 0.1 to 1 mm.
A polymeric resin having an alicyclic structure used in the present invention is superior in moldability, so a thin light guide plate can be molded.
The polymeric resin having an alicyclic structure used in the present invention is superior in moldability, so light guide plates of from a small screen size of about 1 inch to a large screen size of about 20 inches can be molded, and it is preferable when molding a light guide plate of particularly 10 inches or more, because characteristics that a fine pattern of recesses and projections be accurately transferred due to excellent fluidity of the resin.
The polymeric resin having an alicyclic structure used in the present invention has an alicyclic structure at the main chain and/or side chain and it is preferable that the main chain includes the alicyclic structure in terms of mechanical strength and heat resistance, etc.
As the alicyclic structure, there are a cycloalkane structure, cycloalkene structure, etc. From the viewpoint of the mechanical strength, heat resistance, etc., one having a cycloalkane structure is most preferable.
The number of carbon atoms comprising the alicyclic structure is not particularly limited, but is normally 4 to 30, preferably 5 to 20, more preferably 5 to 15, at which time the mechanical strength, the heat resistance and moldability characteristics are well balanced.
The percentage of the repeating units composed of alicyclic structure included in the polymeric resin having an alicyclic structure may be suitably selected in accordance with the object of use, but normally is 30 to 100 wt %, preferably 50 to 100 wt %, more preferably 70 to 100 wt %, most preferably 90 to 100 wt %. If the percentage of the repeating units having an alicyclic structure in the polymeric resin containing an alicyclic structure is excessively small, the heat resistance is inferior, but by containing in the range of 30 to 100 wt %, the mechanical strength, the heat resistance, etc. are well balanced.
Further, the percentage of the repeating units comprised of alicyclic structures without norbornane structures in the whole alicyclic structures in the polymeric resin containing an alicyclic structure used in the present invention may be suitably selected in accordance with the object of use, but the more the more preferable as a light guide plate and is normally at least 10 wt %, preferably at least 20 wt %, more preferably at least 30 wt %. The larger the percentage of repeating units comprised of alicyclic structures without norbornane structures, the better the fluidity and transferability of the resin at molding further improve. Particularly, by having such specific repeating units, the front luminance of the light guide plate to be obtained improves as well as the light resistance, thus, a light guide plate having stable intensified front luminance and little luminance spots to be well balanced can be obtained even by a light exposure from the light source by long time use.
Note that the balance other than the repeating units comprised of alicyclic structures in the polymeric resin containing an alicyclic structure is not particularly limited and is suitably selected in accordance with the object of use.
As specific examples of the polymeric resin containing an alicyclic structure, for example, a norbornene-based polymer, a monocyclic cyclic olefin-based polymer, a cyclic conjugated diene-based polymer, a vinyl alicyclic hydrocarbon polymer, and hydrogenates of the same may be mentioned. Among these, a norbornene-based polymer and a cyclic conjugated diene-based polymer are preferable, and norbornene-based polymer is more preferable.
The norbornene-based polymer is not particularly limited. For example, the polymers disclosed in Japanese Unexamined Patent Publication (Kokai) 1991-14882, Japanese Unexamined Patent Publication (Kokai) 1991-122137, etc. may be used. Specifically, a ring-opening polymer of a norbornene-based monomer and its hydrogenate, an addition polymer of norbornene-based monomers, an addition polymer of a norbornene-based monomer and a copolymerizable vinyl compound, etc. may be mentioned. Among these, a ring-opening polymer of a norbornene-based monomer and its hydrogenate, an addition polymer of norbornene-based monomers, an addition polymer of a norbornene-based monomer and a copolymerizable vinyl compound are preferable. A ring-opening polymer of a norbornene-based monomer and its hydrogenate is particularly preferable. A ring-opening polymer of a norbornene-based monomer and its hydrogenate containing a norbornene-based monomer not having a norbornane ring is further preferable, and hydrogenate of a ring-opening polymer of a norbornene-based monomer containing a norbornene-based monomer not having a norbornane ring is most preferable.
As a norbornene-based monomer, there are ones not having a norbornane ring and ones having one or more norbornane rings.
As norbornene-based monomers not having a norbornane ring, for example, bicyclo[2.2.1]-hept-2-ene (common name norbornene), 5-methyl-bicyclo[2.2.1]-hept-2-ene, 5,5-dimethyl-bicyclo[2.2.1]-hept-2-ene, 5-ethyl-bicyclo[2.2.1]-hept-2-ene, 5-butyl-bicyclo[2.2.1]-hept-2-ene, 5-hexyl-bicyclo[2.2.1]-hept-2-ene, 5-octyl-bicyclo[2.2.1]-hept-2-ene, 5-octadecyl-bicyclo[2.2.1]-hept-2-ene, 5-ethylidene-bicyclo[2.2.1]-hept-2-ene, 5-methylidene-bicyclo[2.2.1]-hept-2-ene, 5-vinyl-bicyclo[2.2.1]-hept-2-ene, 5-propenyl-bicyclo[2.2.1]-hept-2-ene, 5-methoxy-carbonyl-bicyclo[2.2.1]-hept-2-ene, 5-cyano-bicyclo[2.2.1]-hept-2-ene, 5-methyl-5-methoxycarbonyl-bicyclo[2.2.1]-hept-2-ene,
5-methoxycarbonyl-bicyclo[2.2.1]-hept-2-ene, 5-ethoxycarbonyl-bicyclo[2.2.1]-hept-2-ene, 5-methyl-5-ethoxycarbonyl-bicyclo[2.2.1]-hept-2-ene, bicyclo[2.2.1]-hept-5-enyl-2-methylpropionate, bicyclo[2.2.1]-hept-5-enyl-2-methyloctanate, bicyclo[2.2.1]-hept-2-ene-5,6-dicarboxylate anhydride, 5-hydroxymethyl-bicyclo[2.2.1]-hept-2-ene, 5,6-di(hydroxymethyl)-bicyclo[2.2.1]-hept-2-ene, 5-hydroxy-i-propyl-bicyclo[2.2.1]-hept-2-ene, 5,6-dicarboxy-bicyclo[2.2.1]-hept-2-ene, bicyclo[2.2.1]-hept-2-ene-5,6-dicarboxylate imide, 5-cyclopentyl-bicyclo[2.2.1]-hept-2-ene, 5-cyclohexyl-bicyclo[2.2.1]-hept-2-ene, 5-cyclohexenyl-bicyclo[2.2.1]-hept-2-ene, 5-phenyl-bicyclo[2.2.1]-hept-2-ene,
tricyclo[4.3.0.12,5]-deca-3,7-diene (common name dicyclopentadiene), tricyclo[4.3.0.12,5]-deca-3-ene, tricyclo[4.4.0.12,5]-undeca-3,7-diene, tricyclo[4.4.0.12,5]-undeca-3,8-diene, tricyclo[4.4.0.12,5]-undeca-3-ene, tetracyclo[7.4.0.110,13.02,7]-trideca-2,4,6-11-tetraene (also called 1,4-methano-1,4,4a,9a-tetrahydrofluorene), tetracyclo[8.4.0.111,14.03,8]-tetradeca-3,5,7,12-11-tetra ene (also called 1,4-methano-1,4,4a,5,10,10a-hexahydro anthracene), etc. may be mentioned.
As norbornene-based monomers having one or more norbornane rings, for example, tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene (also simply called tetracyclododecene), 8-methyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-ethyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-methylidene-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-ethylidene-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-vinyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-propenyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-methoxycarbonyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-methyl-8-methoxycarbonyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-hydroxymethyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-carboxy-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-cyclopentyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-cyclohexyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-cyclohexenyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, 8-phenyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene, pentacyclo[6.5.1.13,6.02,7.09,13]-pentadeca-3,10-diene, pentacyclo[7.4.0.13,6.110,13.02,7]-pentadeca-4,11-diene, etc. may be mentioned.
These norbornene-based monomers may be used alone or in combinations of two or more types.
The content of a norbornene based monomer not having a norbornane ring in the whole norbornene based monomer may be suitably selected in accordance with the preferable ratio of repeating units composed of alicyclic structures not having the above norbornane structure, but is normally at least 10 wt %, preferably 20 wt %, more preferably 30 wt % and not more than 100 wt %.
As the vinyl compound copolymerizable with norbornene based monomers, for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, and other C2 to C20 ethylene or xcex1-olefins; cyclobutene, cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2-(2-methylbutyl)-1-cyclohexene, cyclooctene, 3a,5,6,7a-tetrahydro-4,7-methano-1H-indene, and other cycloolefins; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,7-octadiene, and other nonconjugated dienes, etc. may be mentioned.
These vinyl-based compounds copolymerizable with norbornene based monomers may be used alone or in combinations of two or more types.
The ring-opening (co)polymer of a norbornene-based monomer may be obtained by causing ring-opening (co)polymerization of a norbornene-based monomer in a solvent or without a solvent normally at a polymerization temperature of xe2x88x9250 to 100xc2x0 C. and a polymerization pressure of 0 to 50 kg/cm2 using as a ring-opening polymerization catalyst a catalyst system comprised of a halide, acetate, or acetylacetone compound of ruthenium, rhodium, palladium, osmium, iridium, platinum, and another metal and a reducing agent or a catalyst system comprised of a halide or acetylacetone compound of titanium, vanadium, zirconium, tungsten, molybdenum, or another metal and an organoaluminum compound. The catalyst system may have added to it molecular oxygen, alcohol, ether, peroxide, carboxylate, an acid anhydride, acid chloride, ester, ketone, nitrogenous compound, sulfurous compound, halide compound, molecular iodine, or other Lewis acid or other tertiary component to enhance the polymerization activity or selectivity of the ring-opening polymerization.
The hydrogenated ring-opening polymer of norbornene-based monomer may be obtained by the method of hydrogenating a ring-opening (co)polymer in the presence of a hydrogenation catalyst by an ordinary method. The hydrogenates are not particularly limited but heterogeneous system catalysts or homogeneous system catalysts are normally used. As the heterogeneous system catalysts, for example, nickel, palladium, platinum, or solid catalysts which makes these metals be carried by a catalyst/carrier of carbon, silica, diatom earth, alumina, titanium oxide, etc.: nickel/silica, nickel/diatom earth, nickel/alumina, palladium/carbon, palladium/silica, palladium/diatom earth, palladium/alumina, etc. may be mentioned. As a homogeneous catalysts, for example, catalysts combined by transition metal compound and alkyl aluminum metal compound or alkyl lithium, such as catalysts combined by cobalt acetic acid/triethyl aluminum, cobalt acetic acid/triisobutyl aluminum, nickel acetic acid/triethyl aluminum, nickel acetic acid/triisobutyl aluminum, nickel acetylacetonato/triethyl aluminum, nickel acetylacetonato/triisobutyl aluminum, titanosenchloride/n-butyl lithium, zirconosenchloride/n-butyl lithium may be mentioned.
These hydrogenated catalysts may be used alone and in combination of two or more types. The use amount of the hydrogenated catalysts in 100 wt % of polymer is normally 0.01 to 100 wt %, preferably 0.1 to 50 wt %, more preferably 1 to 30 wt %. The hydrogenation reaction is performed normally under a hydrogen pressure of 1 to 150 kg/cm2, in a temperature range of 0 to 250xc2x0 C. and a reaction time of 1 to 20 hours. The polymeric resin having an alicyclic structure of the present invention can be obtained by removing the hydrogenated catalyst by filtering after the above hydrogenation reaction and drying to set. When a homogeneous system catalyst was used as the hydrogenation catalyst, it can be obtained by lowering activation of the catalyst by adding alcohol or water to make it insoluble in a solution, then filtering, setting and drying the same.
The addition copolymer of the norbornene-based monomer, norbornene-based monomer and copolymerizable vinyl-based compound may be obtained for example by the method of causing copolymerization of the monomer component in a solvent or without a solvent in the presence of a catalyst system comprised of a titanium, zirconium, or vanadium compound and organoaluminum compound normally at a polymerization temperature of xe2x88x9250 to 100xc2x0 C. and a polymerization pressure of 0 to 50 kg/cm2.
These norbornene based polymers may be used alone or in combinations of two or more types.
As the monocyclic cyclic olefin-based polymer, for example, the addition polymers of cyclohexene, cycloheptene, cyclooctene, and other monocyclic cyclic olefin-based monomers disclosed in Japanese Unexamined Patent Publication (Kokai) 1989-66216 may be mentioned.
As the cyclic conjugated diene-based polymer, for example, the polymers obtained by 1,2- or 1,4-addition polymerization of cyclopentadiene, cyclohexadiene, or other cyclic conjugated diene-based monomers and their hydrogenates etc. disclosed in Japanese Unexamined Patent Publication (Kokai) 1994-136057 or Japanese Unexamined Patent Publication (Kokai) 1995-258318 may be mentioned.
As the vinyl alicyclic hydrocarbon polymer, for example, a polymer of a vinyl cyclohexene or vinyl cyclohexane or other vinyl alicyclic hydrocarbon monomer or its hydrogenate disclosed in Japanese Unexamined Patent Publication (Kokai) 1976-59989, the hydrogenate of the aromatic ring portion of a polymer of a styrene or xcex1-methylstyrene or other vinyl aromatic monomer disclosed in Japanese Unexamined Patent Publication (Kokai) 1988-43910, Japanese Unexamined Patent Publication (Kokai) 1989-1706, etc. may be mentioned.
The molecular weight of the polymeric resin containing an alicyclic structure used in the present invention is suitably selected in accordance with the object of use, but is at least 5000, preferably 5000 to 500000, more preferably 8000 to 200000, particularly preferably 10000 to 100000 in terms of weight average molecular weight (Mw) in a cyclohexane solution (when polymer resin will not dissolve, toluene solution) converted to polyisoprene (converted to styrene in case of toluene solution) measured by gel permeation chromatography, and a molecular weight distribution (Mw/number average molecular weight (Mn)) is 1.0 to 5.0, preferably 1.5 to 4.0, more preferably 1.7 to 3.5, at which time the mechanical strength and moldability are well balanced.
The glass transition temperature (Tg) of the polymeric resin containing an alicyclic structure used in the present invention may be suitably selected in accordance with the object of use, but is preferably high in view of the usage environment and is normally at least 70xc2x0 C., preferably at least 80xc2x0 C., more preferably at least 90xc2x0 C., at which time the heat resistance and the moldability are well balanced.
The melt flow rate (MFR), measured by JIS-K6719 at a temperature of 280xc2x0 C. and a load of 2.16 kgf, of the polymeric resin containing an alicyclic structure used in the present invention may be suitably selected in accordance with the object of use, but is normally 1 to 300 g/10 min., preferably 5 to 250 g/10 min., more preferably 10 to 200 g/10 min. If the melt flow rate is too low, the temperature for heating the molding material at the time of molding becomes higher, so working becomes difficult in some cases, while if too high, burrs and other molding imperfections sometimes occur when molding or the strength becomes insufficient.
The refraction index of the polymeric resin containing an alicyclic structure used in the present invention measured based on the ASTM-D542 at 25xc2x0 C. is normally 1.46 to 1.6, preferably 1.5 to 1.56, more preferably 1.52 to 1.56. The higher the refraction index of a resin used in a light guide plate, the closer to the vertical direction an angle of all reflection becomes, consequently, the reflection direction of an incident light on the reflection surface can be made closer to the vertical direction with respect to the light emission surface and higher luminance can be attained.
The water absorbent rate of the polymeric resin containing an alicyclic structure used in the present invention is normally not more than 0.3%, preferably not more than 0.2%, more preferably not more than 0.1%, at which time a fine pattern formed by the above recesses and projections has little possibility of being deformed by absorbing moisture during used as a light guide plate. Thus, the effect of suppressing luminance spots can be maintained for a long period of time.
Note that polymeric resin containing an alicyclic structure may be used alone or in combinations of two or more types.
In the polymeric resin containing an alicyclic structure used in the present invention, soft polymers, other polymers, various types of compounding agents, fillers may be mixed in it alone or in combinations of two or more types in accordance with need.
The soft polymer indicates a polymer normally having a glass transition temperature (Tg) of not more than 30xc2x0 C., and even polymers having several Tgs or polymers having both a TG and a melting point (Tm) are included in the soft polymers as far as the lowest Tg is not more than 30xc2x0 C.
As such a soft polymer, (a) an olefin-based soft polymer comprised mainly of ethylene, propylene, or another xcex1-olefin, (b) an isobutylene-based soft polymer comprised mainly of isobutylene, (c) a diene-based soft polymer comprised mainly of butadiene, isoprene, or other conjugated diene, (d) a cyclic olefin-based ring-opening polymer comprised mainly of norbornene, cyclopentene, or another cyclic olefin, (e) a soft polymer having a silicon-oxygen bond as a skeleton (organic polysiloxane), (f) a soft polymer comprised mainly of an xcex1xcex2-unsaturated acid and its derivatives, (g) a soft polymer comprised mainly of an unsaturated alcohol and amine or their acyl derivatives or acetal, (h) a polymer of an epoxy compound, (i) flourine-based rubber, (j) other soft polymers, etc. may be mentioned.
As specific examples of these soft polymers, for example, as (a), liquid polyethylene, atactic polypropylene, 1-butene, 4-methyl-1-butene, 1-hexene, 1-octene, and 1-decene and other homo polymers; ethylene-xcex1-olefin copolymers, propylene-xcex1-olefin copolymers, ethylene-propylene-diene copolymers (EPDM), ethylene-cyclic olefin copolymers, ethylene-propylene-styrene copolymers, and other copolymers may be mentioned; as (b), polyisobutylene, isobutylene-isoprene rubber, isobutylene-styrene copolymers, etc. may be mentioned; as (c), polybutadiene, polyisoprene, and other conjugated diene homo polymers; butadiene-styrene random copolymers, isoprene-styrene random copolymers, acrylonitrile-butadiene copolymers, hydrogenates of acrylonitrile-butadiene copolymers, acrylonitrile-butadiene-styrene copolymers, and other random copolymers of conjugated dienes; butadiene-styrene block copolymers, styrene-butadiene-styrene block copolymers, isoprene-styrene block copolymers, styrene-isoprene-styrene block copolymers, and other block copolymers of conjugated dienes and aromatic vinyl-based hydrocarbons, and hydrogenates of these block copolymers may be mentioned;
as (d), norbornene, vinylnorbornene, ethylidene norbornene, and other norbornene-based monomers or cyclobutene, cyclopentene, cyclooctene, and other metathesis ring-opening polymers of monocyclic olefins and their hydrogenates may be mentioned; as (e), dimethyl polysiloxane, diphenyl polysiloxane, dihydroxypolysiloxane, and other silicone rubbers etc. may be mentioned; as (f), polybutylacrylate, polybutylmethacrylate, polyhydroxy ethylmethacrylate, polyacrylamide, polyacrylonitrile, and other acryl monomer homo polymers; and butylacrylate-styrene copolymers and other copolymers of acryl monomers and other monomers may be mentioned;
as (g), polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, polyvinyl benzoate, polyvinyl maleate, and other (esterified) unsaturated alcohol homo polymers; vinyl acetate-styrene copolymers and other copolymers of (esterified) unsaturated alcohols and other monomers etc. may be mentioned.
as (h), polyethylene oxide, polypropylene oxide, epichlorohydrin rubber, etc. may be mentioned; as (i), fluovinylidene-based rubber, tetrafluoride ethylene-propylene rubber, etc. may be mentioned. as (j), natural rubber, polypeptides, proteins, polyester-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, etc. described in the Japanese Unexamined Patent Publication 1996-73709, etc. may be mentioned.
These soft polymers may have cross-linked structures or may have functional groups introduced by modification.
In the present invention, from the viewpoint of giving moisture-resistance in use of a light guide plate under moisture-resistance environment, the soft polymers of (a), (b), and (c) are preferable among the above soft polymers in that they are particular superior in transparency and dispersability after blending. Among these, a diene-based soft polymer is preferable, and hydrogenates of the diene-based soft polymer wherein carbon-carbon unsaturated bonding in units of co-diene bonding is more preferable. As specific examples of these soft polymers, for example, hydrogenates of polybutadiene and other homo polymers; hydrogenates of butadiene-styrene copolymers and other random copolymers; hydrogenates of butadiene-styrene block copolymers, styrene-butadiene-styrene block copolymers, isoprene-styrene block copolymers, styrene-isoprene-styrene block copolymers and other block copolymers; etc. may be mentioned.
Blending amount of soft polymers in polymeric resin having an alicyclic structure is determined so as to give moisture-resistance in use of a light guide plate under a moisture resistance environment, and the weight percentage of the polymer with respect to 100 wt % of polymeric resin having an alicyclic structure is preferably 0.01 to 5 wt %, more preferable, 0.01 to 1 wt %.
As other polymers, for example, polystyrene, poly(metha)acrylate, polycarbonate, polyester, polyether, polyamide, polyimide, polysulfone, etc. may be mentioned. They may be used alone or in combinations of two or more types. The ratio of combination is suitably selected within the range of the objects of the present invention.
Compounding agents are not particularly limited so long as they are ones in general use in the plastic industry, but for example, antioxidants; UV absorbents; light stabilizer; near infrared absorbents; dyes, pigments and other coloring agents; smoother; plasticizers; antistatic agents; fluorescent brightening agents; etc. may be mentioned.
As antioxidants, phenol-based, phosphorus-based, sulfate-based antioxidants, etc. may be mentioned, but among these, phenol-based antioxidant is preferable and alkyl exchange/substitution phenol-based antioxidant is particularly preferable.
As phenol-based antioxidants, those which have been well known may be used, for example, acrylate-based compounds described for example in Japanese Unexamined Patent Publication 1988-179953 and Japanese Unexamined Patent Publication 1989-168643, such as 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methyl benzyl)-4-methylphenyl acrylate, 2,4-di-t-amyl-6-(1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl)phenilacrylate; alkyl exchange/substitution phenol-based compounds, such as, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2xe2x80x2-methylene-bis(4-methyl-6-t-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxy benzyl)benzene, tetrakis(methylene-3-(3xe2x80x2,5xe2x80x2-di-t-butyl-4xe2x80x2-hydroxyphenyl propionate)methane [namely, pentaerythrimethyl-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl propionate)], triethyleneglycol bis(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate), etc.; triazine group contained phenol-based compounds, such as 6-(4-hydroxy-3,5-di-t-butylanilino)-2,4-bisoctylthio-1,3,5-triazine, 4-bisoctylthio-1,3,5-triadin, 2-octylthio-4,6-bis-(3,5-di-t-butyl-4-oxyanilino)-1,3,5-triazine, etc. may be mentioned.
Phosphorus-based antioxidants are not particularly limited so long as they are ones in general use in the plastic industry, but for example, monophosphate-based compounds, such as triphenylphosphate, diphenylisodecyl phosphate, phenyldiisodecyl phosphate, tris(nonylphenyl)phosphate, tris(dinonylphenyl)phosphate, tris(2,4-di-t-butylphenyl)phosphate, 10-(3,5-di-t-butyl-4-hydroxy benzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; diphosphate-based compounds, such as 4,4xe2x80x2-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecylphosphate), 4,4xe2x80x2 isopropylidene-bis(phenyl-di-alkyl(C12 to C,5)phosphate), etc. may be mentioned. Among these, monophosphate-based compounds are preferable and tris(nonylphenyl)phosphate, tris(dinonylphenyl)phosphate, tris(2,4-di-t-butylphenyl)phosphate, etc. are particularly preferable.
As sulfate-based antioxidants, for example, dilauryl 3,3-thiodipropionate, dimyristyl 3,3xe2x80x2-thiodipropipionate, distearyl 3,3-thiodipropionate, laurylstearyl 3,3-thiodipropionate, pentaerythritol-tetrakis-(xcex2-lauryl-thio-propionate), 3,9-bis(2-dodecylthioethyl)-2,4,8,10-tetraoxaspiro[5,5]undecan, etc. may be mentioned.
These antioxidants may be used alone or in combinations of two or more types. The ratio of combination is suitably selected within the range of not interfering with the objects of the present invention, but is normally 0.001 to 5 wt %, preferably 0.01 to 1 wt % with respect to 100 wt % of a polymeric resin having an alicyclic structure.
As UV absorbents, for example, 2-(2-hydroxy-5-methylphenyl)2H-benzotriazole, 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chloro-2H-benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-2H-benzotriazole, 5-chloro-2-(3,5-di-t-butyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(3,5-di-t-amyl-2-hydroxyphenyl)-2H-benzotriazole, and other benzotriazole-based UV absorbents; 4-t-butylphenyl-2-hydroxybenzoate, phenyl-2-hydroxybenzoate, 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate, hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate, 2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)phenol, 2-(2-hydroxy-5-t-octylphenyl)-2H-benzotriazole, 2-(2-hydroxy-4-octylphenyl)-2H-benzotriazole, and other benzoate-based UV absorbents; 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenon-5-sulfonate trihydrate, 2-hydroxy-4-octyloxy-benzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxylbenzophenone, 2,2xe2x80x2-dihydroxy-4,41-dimethoxybenzophenone, and other benzophenone-based UV absorbents; ethyl-2-cyano-3,3-diphenylacrylate, 2xe2x80x2-ethylhexyl-2-cyano-3,3-diphenylacrylate, and other acrylate-based UV absorbents; [2,2xe2x80x2-thiobis(4-t-octylphenolate)]-2-ethylhexylamine nickel and other metal inert complex-based UV absorbents etc. may be mentioned.
As light stabilizers, for example, 2,2,6,6-tetramethyl-4-piperidyl benzoate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-(3,5-di-t-butyl-4-hydroxy benzyl)-2-n-butylmaronate, 4-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)-1-(2-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)ethyl)-2,2,6,6-tetramethylpiperidine, and other hindered amine-based light stabilizers may be mentioned.
As near infrared absorbents, for example, cyanine-based near infrared absorbents; pyrylium-based near infrared absorbents; squaririum-based near infrared absorbents; clochonium-based near infrared absorbents; azulenium-based near infrared absorbents; phthalocyanine-based near infrared absorbents; dithiol metal inert complex-based near infrared absorbents; naphthoquinone-based near infrared absorbents; anthraquinone-based near infrared absorbents; indophenol-based near infrared absorbents; azide-based near infrared absorbents, etc. may be mentioned. Also, near infrared absorbents on the market, such as SIR-103, SIR-114, SIR-128, SIR-130, SIR-132, SIR-152, SIR-159 and SIR-162 (produced by Mitsui Toatsu Chemicals), Kayasorb IR-750, Kayasorb IRG-002, Kayasorb IRG003, IR820B, Kayasorb IRG-022, Kayasorb IRG-023, Kayasorb CY-2, Kayasorb CY-4, Kayasorb CY-9 (produced by Nipppon Kayaku Co.,Ltd.), etc. may be mentioned.
The dye is not particularly limited so long as it uniformly disperses and dissolves in a polymer components, but wide use is made of an oil-soluble dye (various C.I solvent dyes). As specific examples of the oil soluble dues, mention may be made of the various types of C.I. solvent dyes listed in the Color Index, vol. 3, published by the Society of Diyes and Colourists. As the pigment, for example, Pigment Red 38 and other diarylide-based pigments; Pigment Red 48:2, Pigment Red 53, Pigment Red 57:1, and other azo lake-based pigments; Pigment Red 144, Pigment Red 166, Pigment Red 220, Pigment Red 221, Pigment Red 248, and other condensation azo-based pigments; Pigment Red 171, Pigment Red 175, Pigment Red 176, Pigment Red 185, Pigment Red 208, and other benzimidazolone-based pigments; Pigment Red 122 and other quinacridone-based pigments; Pigment Red 149, Pigment Red 178, Pigment Red 179, and other perillene-based pigments; and Pigment Red 177 and other anthraquinone-based pigments may be mentioned. Note that when a light guide plate is required to be colored, either dyes or pigments may be used within the range of the objects of the present invention and is not limited, but in the case of a light guide plate wherein micro-scale optical characteristics matters, coloring by dyes is D preferable. Also, UV absorbents sometimes looks yellow to red color visually and near infrared absorbents sometimes looks black color visually, thus, it is unnecessary to strictly distinguishing these dyes and they may be combined for using.
As smoothing agents, organic compounds, such as esters of aliphatic alcohols and esters of polyhydric alcohol, or partial ester; or inorganic fine particles, etc. may be used. As organic compounds, for example, glyceryl monostearate, glyceryl monolaurate, glyceryl distearate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, etc. may be mentioned. As other smoothing agents, inorganic particles may be generally used. Here, as inorganic fine particles, oxides of 1, 2, 4 and 6 to 14 families of elements in the periodic table, sulfide, hydroxide, nitrogenous substance, haloid, carbonate, hydrosulfate, acetate, phosphate, phosphonate, organic carboxylate, fluosilicate, titanate, fluoboric acid, and particles of their hydrated compounds, complex compound mainly contained by them, natural compounds, etc. may be mentioned.
As plasticizers, for example, phosphate triester-based plasticizers, such as, tricredil phosphate, trixylylphosphate, triphenylphosphate, triethylphenylphosphate, diphenylcredil phosphate, monophenylcredil phosphate, diphenylmonoxylenolphosphate, monophenyldixylenolphosphate, tributylphosphate, triethylphosphate; phthalate plasticizers, such as, dimethyl phthalate, dibutyl phthalate, diheptyl phthalate, phthalic di-n-octyl, phthalic di-2-ethylhexyl, phthalic diisononyl, octyldecyl phthalate, phthalic butyl benzyl; fatty acid monobasic acid ester-based plasticizers, such as, olein acid butyl, glyceryl monoolein acid ester; dihydric alcohol ester-based plasticizers; oxyacid ester-based plasticizers, etc. may be used. Among them, phosphate triester-based plasticizer is preferable and tricredil phosphate, trixylylphosphate are particularly preferable. Furthermore, hydrocarbon polymer being liquid at normal temperature or liquid low molecular weight hydrocarbon are preferably used as a plasticizer. Among them, liquid hydrocarbon polymer of a straight chain state or branch chain state not having a hydrocarbon ring in the main chain is preferable. The weight average molecular weight of the liquid hydrocarbon polymer or liquid low molecular weight hydrocarbon is preferably not more than 10000, more preferably between 200 and 8000, particularly preferably between 300 and 4000. As specific examples of the liquid hydrocarbon polymer, polyisobutene, hydrogenated polybutadiene, hydrogenated polyisoprene, etc. are mentioned. As specific examples of the liquid low molecular weight hydrocarbon, squalane (C30H62, molecular weight=422.8), fluid paraffin (white oil regulated by JIS-K2231 ISO VG10, ISO VG15, ISO VG32, ISO VG68, ISO VG100, VG8 and VG21, etc.) may be mentioned. Among them, squalene, fluid paraffin, polyisobutene are preferable.
As antistatic agents, fatty acid esters of long-chain alkyl alcohol, such as stearyl alcohol, biphenyl alcohol; and polyhydric alcohol, such as glyceryl mono stearate, pentaerythritor monostearate; etc. may be mentioned, but stearyl alcohol and biphenyl alcohol are particularly preferable.
These compounding agents may be used alone or in combinations of two or more types. The ratio of combination is suitably selected within the range of not interfering with the objects of the present invention, but is normally 0.001 to 5 wt %, preferably 0.01 to 1 wt % with respect to 100 wt % of a polymeric resin having an alicyclic structure.